Isaac kehn



chroluie acid eight ounces.

@anat eibiiiire. I,

Letters Patent No. 100,924, dom( lliure/i l5, lhll.

MODE OF PRODUCING PHOTO-LITHOGRAPHIC TRANSFERS.

The Schedule referred tu in lJiese Letters Patent and making part 0f the same.

I, ISAAC REHN, of thecty ot" Washingtoin'anil llistrict ot' Uolnmbia, having invented a new and improved Mode ot" Producing Photo-Lithographie 'lranst'ersy do set fort-h the saine in the ollowing specilication.

The object of my invention is to produee the most perfect', photo-lithographie results by the most simple Aind certain means, and thus extend the application ot' the art to all such requirements as involve the necessity of linear dolineations. 'lo do this l proceed as follows:

Take lof water, thirty-tuo ounces;gelatine, eumarabic, or other oxdizable organic matter, t'our ounces; saturated solution ot' bichromate ot' potassa, or thil equivalent thereof in bichroniate of ammonia or Dissolve the oclatinc, with a gentle heat, in the water, and, after haring removed the solution to a darkened room, add thehiehromate solution and stir the whole together. lt is then ready for use.

\Vith this solution, kept warm, l coat the requisite quantity of paper, with asot't sponge dipped into the solutiou, ai1d spread the saine evenly over one side ol' the paper or other suitable material, then hang it up to dry; or the paper may be tloated on the surlaee ot' the solution, or immersed in it, it' that modo is preferred; but, in either ofthe latter two modes, the solution should be diluted one-third, or thereabout.

This paper, when dry, l expose to the sundight about ten minutes, that the lihn may be thoronghly oxidized, when it is to be collected and preserved l'or subsequent use.

The next step is lo coat thisl paper a second timel with tho warmed glatinous solution, by tloating it on the surl. ot the same in a darkened room, allowing it; to ieurain on until it is thoroughly moisteued, then hang it up to dry, as before, and it, must be kept lioin the light until further used.

When about to use the sheets as above prepared, l Coat them over, in the manner hereinafter described, with aJ preparation made as follows, riz:

'lake of yellow soap, that being the cheapest, and as good for the purpose as any, one ounce; arrow root` starch, or flour, haltan milice; water, one quart; coloring-matter, a sullieient quantity to give the muss a tint which will be visible after it is applied to the paper; saturated solution-ol' biohromate o l' amminonia, two drains, the bchromate of ammonia boing preferred in this case because ot' itsl greater solubility in water than the other bichronmtes, and less water, therefore, introduced into the' compound.

Dissolve` the soap in a pintl of the water by heat, the starch is to be boiled in the remaining pint, then mix the solutions, and evaporate the whole to the cousistenec of thick lithographie ink. The coloring-matter (blue is preferable, because it does not sensibly4 slop Lne action ol' the light) may be added any limi: before the application ot' the compound to the paper. v

When about to appl)- the coating, prot-ced to :i darkened room, and, on :i slab ol' glass-lor stone, add and mix thoroughly the solution ot' biehronmte ol'ammonia with the mass', then, with a roller, on d lo roll upa stone, in thi mannerot lithographie itin't; with this compound; lary the prepared paper on the stone, lin-c down, und pass it through the press. 0n removing` the paper il will be found coated with this sensitized transfer compound. 0r the t'ollowpi/ntr may be substituted tor the method last described, vi/J:

'lalio otgclatine three ounce v soap, three ounces; water thirty ounces; saturated solution ot' bichromate of potassa, twelvel ounces; eriloring-niatter, a sutlicient quantity.

Dissolve the gelatine in one-halll ol' the water by heat, and the soap iu the balance of the water., Mix these two solutions, and, in the. darkened room, add the bichromate solution and the coltiring-matter. On this solution, kept warm, tloat the paper as previously prepared until it is moistened, then hang it up to dry.

l'he paper thus prepared by either dcscribc'dmode is then ready to be placed under a negative, and cxposed to thel action ol' the light, the time being, with a negative ol' moderate strcafth, about live minutes lll U10 Sunlight, or about iiltcen initiates in the. ditfused light ot' a clear day. \\'hen .the action-of the light has been suliicient, which may he known on examination ol' tho print, the li'ame is carried tothe darkened room, where the print is removed, then immersed in tepid water, which will discharge all the material l'roiu the unlightcd portions of the paper except tht` lirst or oxidized layer, and a clear sharp print corresponding with thcl negativo is obtained, which print, when suliicicntly dried, is ready to transt'cr to the stone, zinc, or other suitable material, with out turther manipulation. y

'lhe object in the oxidation ot the tirstlayerou the, paper is to securi` a smooth innnorable basis on which to make the impression, so that the lines may have better and more clear-lv lletined edges.

The purpose oll the lsecond layer is to obtain a soluble layer susceptible of oxidation by the light, by which alst s secured, through the oxidation, the inlsolubility ot' those pm-tioiison which the light has acted, and a retention thereby of the lllS- l MW l'lllllll iu practice that all greasy and untixed inks, or troosten-ring compounds on prints, however perfect these prints may be when ready for the stone, are more. or less mashed iu the act of transferring them l to the stone, by which the lines are thickened, broken. and the work choker] np, rendering the rcsults'comi paratircly imperfect. l have sought-"to avoid this b v preparing and employing a transfer' compound sensitive to the action of light, by which this transfer ma.- terial may also be oxidized, and thus solidified and fixed.

In the employment of the organic mordant in couibination with the oxidizingagcnt and the transferring substance, I have secured a sure means of avoiding the mashing in the nely of transfer', and so perfectly is this obtained by my process that no'amount of pressure I have been able to bring to hear on these transfers by the lithographie press, not even when passed through several times in succession, shows any signs of the spreading of the lines, while the transfer thus made readily receives the ink, and all therqualities necessary for printing are secured. The purpose ofthis third layer will, therefore, be evident.

lhe object in the introduction ofthe coloring-matter to the transfer compound is to enable the operator to see distinctly the progress of the discharge of the described.

ISAAC REHN.

Witnesses: l

W. B. FRENCH, G. W. PnILLIPs. 

